An antenna module (10) includes a ground electrode (30) in which a slit (33) is formed in such a manner as to form an opening along a perimeter of the ground electrode, a first antenna (110) and a second antenna (110A) arranged in or on the ground electrode (30), and a coupling reducing electrode (200) connected to the ground electrode (30) within the slit (33). The slit (33) is formed on a path leading from the first antenna (110) to the second antenna (110A) along the perimeter of the ground electrode. The coupling reducing electrode (200) includes a first conductor (220) having a length corresponding to a first frequency and a second conductor (230) having a length corresponding to a second frequency, which is higher than the first frequency.